1. Field of the Invention
This invention relates to a sterilization solution, termed a use-dilution solution, capable of sterilizing at room temperature, a multi-part or two-part concentrate system suitable for preparing the use-dilution solution, a method for preparing the use-dilution solution, and a method of sterilizing with the use-dilution solution. This invention also relates to an anti-corrosive agent suitable for use in the microbicide of the present invention.
2. Description of Related Art
Conventionally, medical instruments have been sterilized or disinfected by introducing them into a high temperature/high pressure autoclave. Despite their effectiveness in killing microorganisms and the like, autoclaves are associated with several significant disadvantages. There are high capital and maintenance costs of autoclaves. Moreover, many medical instruments cannot withstand the high temperature and pressures associated with autoclave use. Another drawback is the cycle time of autoclaves, which may last for anywhere from several minutes to several hours.
As an alternative to autoclaves, ethylene oxide gas has been used in sealed sterilization chambers operated at elevated pressures. However, this conventional method is plagued by long cycle times, requiring long exposure times in a vacuum and even longer aeration times. Further, ethylene oxide gas is not effective in sterilizing all types of medical devices, and is highly toxic.
In order to circumvent some of the problems associated with autoclaves and ethylene oxide gas chambers, liquid sterilization solutions have been proposed. However, many conventional liquid sterilants require relatively long immersion times in order to assure sterilization as measured by elimination of bacterial endospore viability. For example, gluteraldehyde, a conventional sterilant which causes respiratory problems, takes 10 hours at room temperature for 100% kill of bacterial endospores. Moreover, many liquid sterilants are unacceptably corrosive, even those containing corrosion inhibitors, especially with respect to metal parts, particularly brass, copper, and aluminum.
It is therefore an object of this invention to overcome the above-mentioned problems by providing an anti-microbial, use-dilution sterilization solution that is capable of sterilizing objects containing bacterial spores, at room temperature, yet exhibits superior anti-corrosive properties.
In accordance with the principles of this invention, these and other objects are achieved by providing a multi-part concentrate system having a first component comprising hydrogen peroxide and water and a second component comprising formic acid and water. The first and second components are separate from each other. The system also includes a block copolymer of ethylene oxide and propylene oxide, phosphoric acid and benzotriazole, wherein each of the block copolymer, phosphoric acid and benzotriazole can be present in the first or second components. Typically, the first component contains 50 wt % hydrogen peroxide, 2.3 wt % C-99 with the remainder water; and the second component contains 25 wt % formic acid, 3.3 wt % L-44, 5.0 wt % phosphoric acid and the remainder water.
The first component and the second component are mixed together to form an initial activated sterilization solution which at time zero contains 30 wt % hydrogen peroxide, 10 wt % formic acid, 1.38 wt % C-99, 1.38 wt % L-44 and 2.0 wt % phosphoric acid.
When the initial activated sterilization solution reaches equilibrium, the resulting activated solution contains 25 wt % hydrogen peroxide, 6.5 wt % formic acid, 4.5-5.0 wt % performic acid, 1.38 wt % C-99, 1.38 wt % L-44, 2.0 wt % phosphoric acid and the remainder water. The resulting activated solution comprises about 30 wt % to about 40 wt % of an active anti-microbial composition and about 70 wt % to about 60 wt % water.
The resulting activated solution is further diluted with water to form a use-dilution solution that is used for sterilizing. The use-dilution solution comprises:
about 0.05 wt % to about 0.5 wt % performic acid, more preferably about 0.1 wt % to 0.5 wt % and most preferably 0.3 wt %;
about 0.4 wt % to about 6.0 wt % hydrogen peroxide, more preferably about 3.0 wt % to about 6.0 wt % and most preferably about 5.0 wt % to about 5.5 wt %;
preferably about 0.07 wt % to about 1.5 wt % formic acid, and most preferably about 0.05 wt % to 1.5 wt %;
preferably about 0.1 wt % to about 1.0 wt % benzotriazole, and most preferably 0.2 wt %;
preferably about 0.1 wt % to about 0.5 wt % and more preferably 0.2 wt % block copolymer of ethylene oxide and propylene oxide (also referred to herein as a polyoxypropylene-polyoxyethylene block copolymer); and
preferably about 0.1 wt % to about 0.5 wt % phosphoric acid, and most preferably 0.3 wt %.
The anti-microbial composition use-dilution solution of the invention is useful as a sterilant. Sterilization means the absence of all detectable life forms, whether pathogenic or not. That is, sterilization means that a 100% kill of bacterial endospores is achieved. Sterilization is different than disinfection, which means the absence of pathogenic life forms. Thus, a sterilized instrument is also disinfected; however, the converse is not true: a disinfected instrument is not always sterilized.
Another object of this invention is to provide a two-part concentrate system or multi-part concentrate anti-microbial system, which is concentrated so as to facilitate storage, shelf-life and transfer, yet which can be diluted into a use-dilution sterilization solution which achieves a 100% kill of microorganisms including bacterial spores at room temperature.
In accordance with the principles of this invention, this and other objects can be achieved by the provision of a multi-part concentrate system which broadly includes: a first component comprising hydrogen peroxide and water; a second component comprising formic acid and water; also present as part of the multi-part concentrate system are a polyoxypropylene-polyoxyethylene block copolymer (also referred to herein as a block copolymer of ethylene oxide and propylene oxide); phosphoric acid; benzotriazole; and water. The block copolymer, phosphoric acid, and benzotriazole may be present in the first component and/or second component independently of one another or in a third component.
This invention also involves a method of making an activated intermediary solution from the above-described multi-part or two-part concentrate system. Specifically, when the two components of the two-part system are mixed together at appropriate ratios and diluted with water, an activated sterilization solution results that has reduced corrosive properties and can function as a sterilant upon further dilution to a use-dilution solution.
This invention further relates to a method of sterilizing a substrate, especially medical equipment, with the above-mentioned sterilization solution. In this regard, this method is especially suitable for sterilizing an object contaminated with bacterial spores, and may effectively be utilized at room temperature if desired. However, it is possible to use a temperature of from 45-55xc2x0 C. to accelerate the active solution and to enhance efficacy of the use-dilution solution.
This invention still further relates to an anti-corrosive agent comprising phosphoric acid, block copolymer and benzotriazole. The anti-corrosive agent is suitable for use with anti-microbial compositions, especially compositions comprising performic acid, formic acid, and hydrogen peroxide.
These and other objects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of this invention.